1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
26 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
27
28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
29 #include "memory/collectorPolicy.hpp"
30 #include "memory/generation.hpp"
31 #include "memory/sharedHeap.hpp"
32
33 class SubTasksDone;
34
35 // A "GenCollectedHeap" is a SharedHeap that uses generational
36 // collection. It has two generations, young and old.
37 class GenCollectedHeap : public SharedHeap {
38 friend class GenCollectorPolicy;
39 friend class Generation;
40 friend class DefNewGeneration;
41 friend class TenuredGeneration;
42 friend class ConcurrentMarkSweepGeneration;
43 friend class CMSCollector;
44 friend class GenMarkSweep;
45 friend class VM_GenCollectForAllocation;
46 friend class VM_GenCollectFull;
47 friend class VM_GenCollectFullConcurrent;
48 friend class VM_GC_HeapInspection;
49 friend class VM_HeapDumper;
50 friend class HeapInspection;
51 friend class GCCauseSetter;
52 friend class VMStructs;
53 public:
54 friend class VM_PopulateDumpSharedSpace;
55
56 protected:
57 // Fields:
58 static GenCollectedHeap* _gch;
59
60 private:
61 Generation* _young_gen;
62 Generation* _old_gen;
63
64 // The generational collector policy.
65 GenCollectorPolicy* _gen_policy;
66
67 // Indicates that the most recent previous incremental collection failed.
68 // The flag is cleared when an action is taken that might clear the
69 // condition that caused that incremental collection to fail.
70 bool _incremental_collection_failed;
71
72 // In support of ExplicitGCInvokesConcurrent functionality
73 unsigned int _full_collections_completed;
74
75 // Data structure for claiming the (potentially) parallel tasks in
76 // (gen-specific) roots processing.
77 SubTasksDone* _gen_process_roots_tasks;
78 SubTasksDone* gen_process_roots_tasks() { return _gen_process_roots_tasks; }
79
80 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
81 bool run_verification, bool clear_soft_refs);
82
83 // In block contents verification, the number of header words to skip
84 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
85
86 protected:
87 // Helper functions for allocation
88 HeapWord* attempt_allocation(size_t size,
89 bool is_tlab,
90 bool first_only);
91
92 // Helper function for two callbacks below.
93 // Considers collection of the first max_level+1 generations.
94 void do_collection(bool full,
95 bool clear_all_soft_refs,
96 size_t size,
97 bool is_tlab,
98 int max_level);
99
100 // Callback from VM_GenCollectForAllocation operation.
101 // This function does everything necessary/possible to satisfy an
102 // allocation request that failed in the youngest generation that should
103 // have handled it (including collection, expansion, etc.)
104 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
105
106 // Callback from VM_GenCollectFull operation.
107 // Perform a full collection of the first max_level+1 generations.
108 virtual void do_full_collection(bool clear_all_soft_refs);
109 void do_full_collection(bool clear_all_soft_refs, int max_level);
110
111 // Does the "cause" of GC indicate that
112 // we absolutely __must__ clear soft refs?
113 bool must_clear_all_soft_refs();
114
115 public:
116 GenCollectedHeap(GenCollectorPolicy *policy);
117
118 GCStats* gc_stats(int level) const;
119
120 // Returns JNI_OK on success
121 virtual jint initialize();
122
123 char* allocate(size_t alignment,
124 size_t* _total_reserved, int* _n_covered_regions,
125 ReservedSpace* heap_rs);
126
127 // Does operations required after initialization has been done.
128 void post_initialize();
129
130 // Initialize ("weak") refs processing support
131 virtual void ref_processing_init();
132
133 virtual CollectedHeap::Name kind() const {
134 return CollectedHeap::GenCollectedHeap;
135 }
136
137 Generation* young_gen() const { return _young_gen; }
138 Generation* old_gen() const { return _old_gen; }
139
140 // The generational collector policy.
141 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
142
143 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
144
145 // Adaptive size policy
146 virtual AdaptiveSizePolicy* size_policy() {
147 return gen_policy()->size_policy();
148 }
149
150 // Return the (conservative) maximum heap alignment
151 static size_t conservative_max_heap_alignment() {
152 return Generation::GenGrain;
153 }
154
155 size_t capacity() const;
156 size_t used() const;
157
158 // Save the "used_region" for generations level and lower.
159 void save_used_regions(int level);
160
161 size_t max_capacity() const;
162
163 HeapWord* mem_allocate(size_t size,
164 bool* gc_overhead_limit_was_exceeded);
165
166 // We may support a shared contiguous allocation area, if the youngest
167 // generation does.
168 bool supports_inline_contig_alloc() const;
169 HeapWord** top_addr() const;
170 HeapWord** end_addr() const;
171
172 // Does this heap support heap inspection? (+PrintClassHistogram)
173 virtual bool supports_heap_inspection() const { return true; }
174
175 // Perform a full collection of the heap; intended for use in implementing
176 // "System.gc". This implies as full a collection as the CollectedHeap
177 // supports. Caller does not hold the Heap_lock on entry.
178 void collect(GCCause::Cause cause);
179
180 // The same as above but assume that the caller holds the Heap_lock.
181 void collect_locked(GCCause::Cause cause);
182
183 // Perform a full collection of the first max_level+1 generations.
184 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
185 void collect(GCCause::Cause cause, int max_level);
186
187 // Returns "TRUE" iff "p" points into the committed areas of the heap.
188 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
189 // be expensive to compute in general, so, to prevent
190 // their inadvertent use in product jvm's, we restrict their use to
191 // assertion checking or verification only.
192 bool is_in(const void* p) const;
193
194 // override
195 bool is_in_closed_subset(const void* p) const {
196 if (UseConcMarkSweepGC) {
197 return is_in_reserved(p);
198 } else {
199 return is_in(p);
200 }
201 }
202
203 // Returns true if the reference is to an object in the reserved space
204 // for the young generation.
205 // Assumes the the young gen address range is less than that of the old gen.
206 bool is_in_young(oop p);
207
208 #ifdef ASSERT
209 virtual bool is_in_partial_collection(const void* p);
210 #endif
211
212 virtual bool is_scavengable(const void* addr) {
213 return is_in_young((oop)addr);
214 }
215
216 // Iteration functions.
217 void oop_iterate(ExtendedOopClosure* cl);
218 void object_iterate(ObjectClosure* cl);
219 void safe_object_iterate(ObjectClosure* cl);
220 Space* space_containing(const void* addr) const;
221
222 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
223 // each address in the (reserved) heap is a member of exactly
224 // one block. The defining characteristic of a block is that it is
225 // possible to find its size, and thus to progress forward to the next
226 // block. (Blocks may be of different sizes.) Thus, blocks may
227 // represent Java objects, or they might be free blocks in a
228 // free-list-based heap (or subheap), as long as the two kinds are
229 // distinguishable and the size of each is determinable.
230
231 // Returns the address of the start of the "block" that contains the
232 // address "addr". We say "blocks" instead of "object" since some heaps
233 // may not pack objects densely; a chunk may either be an object or a
234 // non-object.
235 virtual HeapWord* block_start(const void* addr) const;
236
237 // Requires "addr" to be the start of a chunk, and returns its size.
238 // "addr + size" is required to be the start of a new chunk, or the end
239 // of the active area of the heap. Assumes (and verifies in non-product
240 // builds) that addr is in the allocated part of the heap and is
241 // the start of a chunk.
242 virtual size_t block_size(const HeapWord* addr) const;
243
244 // Requires "addr" to be the start of a block, and returns "TRUE" iff
245 // the block is an object. Assumes (and verifies in non-product
246 // builds) that addr is in the allocated part of the heap and is
247 // the start of a chunk.
248 virtual bool block_is_obj(const HeapWord* addr) const;
249
250 // Section on TLAB's.
251 virtual bool supports_tlab_allocation() const;
252 virtual size_t tlab_capacity(Thread* thr) const;
253 virtual size_t tlab_used(Thread* thr) const;
254 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
255 virtual HeapWord* allocate_new_tlab(size_t size);
256
257 // Can a compiler initialize a new object without store barriers?
258 // This permission only extends from the creation of a new object
259 // via a TLAB up to the first subsequent safepoint.
260 virtual bool can_elide_tlab_store_barriers() const {
261 return true;
262 }
263
264 virtual bool card_mark_must_follow_store() const {
265 return UseConcMarkSweepGC;
266 }
267
268 // We don't need barriers for stores to objects in the
269 // young gen and, a fortiori, for initializing stores to
270 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
271 // only and may need to be re-examined in case other
272 // kinds of collectors are implemented in the future.
273 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
274 // We wanted to assert that:-
275 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
276 // "Check can_elide_initializing_store_barrier() for this collector");
277 // but unfortunately the flag UseSerialGC need not necessarily always
278 // be set when DefNew+Tenured are being used.
279 return is_in_young(new_obj);
280 }
281
282 // The "requestor" generation is performing some garbage collection
283 // action for which it would be useful to have scratch space. The
284 // requestor promises to allocate no more than "max_alloc_words" in any
285 // older generation (via promotion say.) Any blocks of space that can
286 // be provided are returned as a list of ScratchBlocks, sorted by
287 // decreasing size.
288 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
289 // Allow each generation to reset any scratch space that it has
290 // contributed as it needs.
291 void release_scratch();
292
293 // Ensure parsability: override
294 virtual void ensure_parsability(bool retire_tlabs);
295
296 // Time in ms since the longest time a collector ran in
297 // in any generation.
298 virtual jlong millis_since_last_gc();
299
300 // Total number of full collections completed.
301 unsigned int total_full_collections_completed() {
302 assert(_full_collections_completed <= _total_full_collections,
303 "Can't complete more collections than were started");
304 return _full_collections_completed;
305 }
306
307 // Update above counter, as appropriate, at the end of a stop-world GC cycle
308 unsigned int update_full_collections_completed();
309 // Update above counter, as appropriate, at the end of a concurrent GC cycle
310 unsigned int update_full_collections_completed(unsigned int count);
311
312 // Update "time of last gc" for all generations to "now".
313 void update_time_of_last_gc(jlong now) {
314 _young_gen->update_time_of_last_gc(now);
315 _old_gen->update_time_of_last_gc(now);
316 }
317
318 // Update the gc statistics for each generation.
319 // "level" is the level of the latest collection.
320 void update_gc_stats(int current_level, bool full) {
321 _young_gen->update_gc_stats(current_level, full);
322 _old_gen->update_gc_stats(current_level, full);
323 }
324
325 // Override.
326 bool no_gc_in_progress() { return !is_gc_active(); }
327
328 // Override.
329 void prepare_for_verify();
330
331 // Override.
332 void verify(bool silent, VerifyOption option);
333
334 // Override.
335 virtual void print_on(outputStream* st) const;
336 virtual void print_gc_threads_on(outputStream* st) const;
337 virtual void gc_threads_do(ThreadClosure* tc) const;
338 virtual void print_tracing_info() const;
339 virtual void print_on_error(outputStream* st) const;
340
341 // PrintGC, PrintGCDetails support
342 void print_heap_change(size_t prev_used) const;
343
344 // The functions below are helper functions that a subclass of
345 // "CollectedHeap" can use in the implementation of its virtual
346 // functions.
347
348 class GenClosure : public StackObj {
349 public:
350 virtual void do_generation(Generation* gen) = 0;
351 };
352
353 // Apply "cl.do_generation" to all generations in the heap
354 // If "old_to_young" determines the order.
355 void generation_iterate(GenClosure* cl, bool old_to_young);
356
357 void space_iterate(SpaceClosure* cl);
358
359 // Return "true" if all generations have reached the
360 // maximal committed limit that they can reach, without a garbage
361 // collection.
362 virtual bool is_maximal_no_gc() const;
363
364 // Convenience function to be used in situations where the heap type can be
365 // asserted to be this type.
366 static GenCollectedHeap* heap();
367
368 void set_par_threads(uint t);
369
370 // Invoke the "do_oop" method of one of the closures "not_older_gens"
371 // or "older_gens" on root locations for the generation at
372 // "level". (The "older_gens" closure is used for scanning references
373 // from older generations; "not_older_gens" is used everywhere else.)
374 // If "younger_gens_as_roots" is false, younger generations are
375 // not scanned as roots; in this case, the caller must be arranging to
376 // scan the younger generations itself. (For example, a generation might
377 // explicitly mark reachable objects in younger generations, to avoid
378 // excess storage retention.)
379 // The "so" argument determines which of the roots
380 // the closure is applied to:
381 // "SO_None" does none;
382 private:
383 void gen_process_roots(int level,
384 bool younger_gens_as_roots,
385 bool activate_scope,
386 SharedHeap::ScanningOption so,
387 OopsInGenClosure* not_older_gens,
388 OopsInGenClosure* weak_roots,
389 OopsInGenClosure* older_gens,
390 CLDClosure* cld_closure,
391 CLDClosure* weak_cld_closure,
392 CodeBlobClosure* code_closure);
393
394 public:
395 static const bool StrongAndWeakRoots = false;
396 static const bool StrongRootsOnly = true;
397
398 void gen_process_roots(int level,
399 bool younger_gens_as_roots,
400 bool activate_scope,
401 SharedHeap::ScanningOption so,
402 bool only_strong_roots,
403 OopsInGenClosure* not_older_gens,
404 OopsInGenClosure* older_gens,
405 CLDClosure* cld_closure);
406
407 // Apply "root_closure" to all the weak roots of the system.
408 // These include JNI weak roots, string table,
409 // and referents of reachable weak refs.
410 void gen_process_weak_roots(OopClosure* root_closure);
411
412 // Set the saved marks of generations, if that makes sense.
413 // In particular, if any generation might iterate over the oops
414 // in other generations, it should call this method.
415 void save_marks();
416
417 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
418 // allocated since the last call to save_marks in generations at or above
419 // "level". The "cur" closure is
420 // applied to references in the generation at "level", and the "older"
421 // closure to older generations.
422 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
423 void oop_since_save_marks_iterate(int level, \
424 OopClosureType* cur, \
425 OopClosureType* older);
426
427 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
428
429 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
430
431 // Returns "true" iff no allocations have occurred in any generation at
432 // "level" or above since the last
433 // call to "save_marks".
434 bool no_allocs_since_save_marks(int level);
435
436 // Returns true if an incremental collection is likely to fail.
437 // We optionally consult the young gen, if asked to do so;
438 // otherwise we base our answer on whether the previous incremental
439 // collection attempt failed with no corrective action as of yet.
440 bool incremental_collection_will_fail(bool consult_young) {
441 // Assumes a 2-generation system; the first disjunct remembers if an
442 // incremental collection failed, even when we thought (second disjunct)
443 // that it would not.
444 assert(heap()->collector_policy()->is_generation_policy(),
445 "the following definition may not be suitable for an n(>2)-generation system");
446 return incremental_collection_failed() ||
447 (consult_young && !_young_gen->collection_attempt_is_safe());
448 }
449
450 // If a generation bails out of an incremental collection,
451 // it sets this flag.
452 bool incremental_collection_failed() const {
453 return _incremental_collection_failed;
454 }
455 void set_incremental_collection_failed() {
456 _incremental_collection_failed = true;
457 }
458 void clear_incremental_collection_failed() {
459 _incremental_collection_failed = false;
460 }
461
462 // Promotion of obj into gen failed. Try to promote obj to higher
463 // gens in ascending order; return the new location of obj if successful.
464 // Otherwise, try expand-and-allocate for obj in both the young and old
465 // generation; return the new location of obj if successful. Otherwise, return NULL.
466 oop handle_failed_promotion(Generation* old_gen,
467 oop obj,
468 size_t obj_size);
469
470 private:
471 // Accessor for memory state verification support
472 NOT_PRODUCT(
473 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
474 )
475
476 // Override
477 void check_for_non_bad_heap_word_value(HeapWord* addr,
478 size_t size) PRODUCT_RETURN;
479
480 // For use by mark-sweep. As implemented, mark-sweep-compact is global
481 // in an essential way: compaction is performed across generations, by
482 // iterating over spaces.
483 void prepare_for_compaction();
484
485 // Perform a full collection of the first max_level+1 generations.
486 // This is the low level interface used by the public versions of
487 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
488 void collect_locked(GCCause::Cause cause, int max_level);
489
490 // Returns success or failure.
491 bool create_cms_collector();
492
493 // In support of ExplicitGCInvokesConcurrent functionality
494 bool should_do_concurrent_full_gc(GCCause::Cause cause);
495 void collect_mostly_concurrent(GCCause::Cause cause);
496
497 // Save the tops of the spaces in all generations
498 void record_gen_tops_before_GC() PRODUCT_RETURN;
499
500 protected:
501 virtual void gc_prologue(bool full);
502 virtual void gc_epilogue(bool full);
503 };
504
505 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP